High-linearity receiver with transmit leakage cancellation

Abstract

Techniques for performing transmit (TX) leakage cancellation are described. A receiver includes a low noise amplifier (LNA) and a TX leakage canceller. The LNA amplifies a receiver input signal and provides an amplified signal. The TX leakage canceller includes a downconverter, a notch filter, and an upconverter. The downconverter downconverts a canceller input signal (e.g., obtained from the LNA output) with a first LO signal at a transmit frequency and provides a downconverted signal. The notch filter filters the downconverted signal to pass an undesired signal (e.g., a TX leakage signal) and attenuate a jammer and a desired signal in the canceller input signal. The upconverter upconverts the filtered signal with a second LO signal at the transmit frequency and provides a feedback signal. The feedback signal is subtracted at the input or output of the LNA to cancel the undesired signal.

What is claimed is: 
     
       1. An apparatus comprising:
 a downconverter to downconvert at a receive frequency an amplified signal based on an input signal and provide a downconverted signal; 
 a notch filter to filter at a frequency different than the receive frequency the downconverted signal and provide a filtered signal; 
 an upconverter to upconvert the filtered signal and provide a feedback signal; and 
 a summer to cancel an undesired signal in the input signal based on the feedback signal. 
 
     
     
       2. The apparatus of  claim 1 , further comprising:
 a low noise amplifier (LNA) to amplify a receiver input signal and provide the amplified signal, and the feedback signal being subtracted at an input of the LNA. 
 
     
     
       3. The apparatus of  claim 1 , further comprising:
 a low noise amplifier (LNA) to amplify a receiver input signal and provide a first amplified signal; and 
 a transconductance amplifier to amplify the first amplified signal and provide a second amplified signal, the amplified signal being obtained based on the second amplified signal, and the feedback signal being subtracted at an input of the LNA or an output of the LNA. 
 
     
     
       4. The apparatus of  claim 1 , the downconverter downconverting the amplified signal with a first local oscillator (LO) signal at a transmit frequency and providing the downconverted signal, and the upconverter upconverting the filtered signal with a second LO signal at the transmit frequency and providing the feedback signal. 
     
     
       5. The apparatus of  claim 1 , the downconverter comprising:
 a first mixer to downconvert the amplified signal with an inphase local oscillator (LO) signal and provide an inphase downconverted signal, and 
 a second mixer to downconvert the amplified signal with a quadrature LO signal and provide a quadrature downconverted signal. 
 
     
     
       6. The apparatus of  claim 5 , the notch filter comprising:
 a first section to filter the inphase downconverted signal and provide an inphase filtered signal, and 
 a second section to filter the quadrature downconverted signal and provide a quadrature filtered signal. 
 
     
     
       7. The apparatus of  claim 6 , the notch filter further comprising:
 a first capacitor to couple a first intermediate signal from the first section to the second section, and 
 a second capacitor to couple a second intermediate signal from the second section to the first section. 
 
     
     
       8. The apparatus of  claim 6 , the upconverter comprising:
 a third mixer to upconvert the inphase filtered signal with the inphase LO signal, 
 a fourth mixer to upconvert the quadrature filtered signal with the quadrature LO signal, and 
 another summer to sum outputs of the third and fourth mixers and provide the feedback signal. 
 
     
     
       9. The apparatus of  claim 1 , the undesired signal comprising a transmit (TX) leakage signal from a transmitter, and the notch filter passing the TX leakage signal. 
     
     
       10. The apparatus of  claim 1 , the notch filter attenuating a jammer and a desired signal in the input signal. 
     
     
       11. The apparatus of  claim 1 , the notch filter having a passband equal to or larger than a bandwidth of the undesired signal and providing a predetermined amount of attenuation of a desired signal in the input signal. 
     
     
       12. The apparatus of  claim 1 , further comprising:
 a gm-C circuit implementing the notch filter and comprising a plurality of transconductance amplifiers, a plurality of resistors, and a plurality of capacitors having values determined based on a bandwidth and a notch frequency of the notch filter. 
 
     
     
       13. The apparatus of  claim 1 , further comprising:
 an active-RC circuit implementing the notch filter and comprising a plurality of operational amplifiers, a plurality of resistors, and a plurality of capacitors having values determined based on a bandwidth and a notch frequency of the notch filter. 
 
     
     
       14. The apparatus of  claim 1 , the notch filter comprising a complex notch filter having a notch only at positive frequency or negative frequency. 
     
     
       15. The apparatus of  claim 1 , the notch filter having a notch at a frequency determined by a difference between the receive frequency and a transmit frequency. 
     
     
       16. The apparatus of  claim 1 , the notch filter having a notch at a frequency of a jammer in the input signal. 
     
     
       17. The apparatus of  claim 1 , wherein the downconverter couples to the notch filter, and the notch filter couples to the upconverter, and the upconverter couples to the summer. 
     
     
       18. An integrated circuit comprising:
 a downconverter to downconvert at a receive frequency an amplified signal based on an input signal and provide a downconverted signal; 
 a notch filter to filter at a frequency different than the receive frequency the downconverted signal and provide a filtered signal; 
 an upconverter to upconvert the filtered signal and provide a feedback signal; and 
 a summer to cancel an undesired signal in the input signal based on the feedback signal. 
 
     
     
       19. The integrated circuit of  claim 18 , further comprising:
 a low noise amplifier (LNA) to amplify a receiver input signal and provide the amplified signal, and the feedback signal being subtracted at an input of the LNA. 
 
     
     
       20. The integrated circuit of  claim 18 , the downconverter downconverting the amplified signal with a first local oscillator (LO) signal at a transmit frequency and providing the downconverted signal, and the upconverter upconverting the filtered signal with a second LO signal at the transmit frequency and providing the feedback signal. 
     
     
       21. The integrated circuit of  claim 18 , the notch filter passing the undesired signal and attenuating a jammer and a desired signal in the input signal. 
     
     
       22. A wireless device comprising:
 a receiver to process a receiver input signal and provide a canceller input signal; and 
 a canceller to downconvert at a receive frequency an amplified signal based on the canceller input signal to obtain a downconverted signal, to filter at a frequency different than the receive frequency the downconverted signal with a notch filter to obtain a filtered signal, to upconvert the filtered signal to obtain a feedback signal, and to cancel an undesired signal in the receiver input signal based on the feedback signal. 
 
     
     
       23. The wireless device of  claim 22 , the notch filter passing the undesired signal and attenuating a jammer and a desired signal in the input signal. 
     
     
       24. A method comprising:
 downconverting at a receive frequency an amplified signal based on an input signal to obtain a downconverted signal; 
 filtering at a frequency different than the receive frequency the downconverted signal with a notch filter to obtain a filtered signal; 
 upconverting the filtered signal to obtain a feedback signal; and 
 canceling an undesired signal in the input signal based on the feedback signal. 
 
     
     
       25. The method of  claim 24 , the downconverting the amplified signal comprising downconverting the input signal with a first local oscillator (LO) signal at a transmit frequency, and the upconverting the filtered signal comprising upconverting the filtered signal with a second LO signal at the transmit frequency. 
     
     
       26. The method of  claim 24 , further comprising:
 amplifying a receiver input signal to obtain the amplified signal; and 
 subtracting the feedback signal from the receiver input signal to cancel the undesired signal in the input signal. 
 
     
     
       27. The method of  claim 24 , the filtering the downconverted signal with the notch filter comprising:
 passing the undesired signal component in the input signal, and 
 attenuating a jammer and a desired signal in the input signal. 
 
     
     
       28. An apparatus comprising:
 means for downconverting at a receive frequency an amplified signal based on an input signal to obtain a downconverted signal; 
 means for filtering at a frequency different than the receive frequency the downconverted signal with a notch filter to obtain a filtered signal; 
 means for upconverting the filtered signal to obtain a feedback signal; and 
 means for canceling an undesired signal in the input signal based on the feedback signal. 
 
     
     
       29. The apparatus of  claim 28 , the means for downconverting the amplified signal comprising means for downconverting the amplified signal with a first local oscillator (LO) signal at a transmit frequency, and the means for upconverting the filtered signal comprising means for upconverting the filtered signal with a second LO signal at the transmit frequency. 
     
     
       30. The apparatus of  claim 28 , further comprising:
 means for amplifying a receiver input signal to obtain the amplified signal; and 
 means for subtracting the feedback signal from the receiver input signal to cancel the undesired signal in the input signal. 
 
     
     
       31. The apparatus of  claim 28 , the means for filtering the downconverted signal with the notch filter comprising:
 means for passing the undesired signal component in the input signal, and 
 means for attenuating a jammer and a desired signal in the input signal.